Impact of a Sewage Treatment Plant on Health of Local Residents: Gastrointestinal System Symptoms

Abstract

The aim of this study was to evaluate the impact of a sewage treatment plant on the occurrence of gastrointestinal symptoms among the local residents. A survey was conducted on two populations: one from the vicinity of the sewage treatment plant (the exposed group: 586 people), and the other from outside the impact area of the plant (the control group: 502 people). The research area was divided into distance zones from the plant (A, B, C). The questionnaire included questions about the occurrence of gastrointestinal disorders. Compared with the control group, the local residents reported more often: nausea, vomiting, and frequent diarrhea Occurrences of gastrointestinal disorders were associated with air pollution by pathogenic staphylococci (OR similar to 7) and odours (OR = 7.34; Cl 3.43-15.72) emitted by the plant, and also living in zone A vs. zone C (OR = 3.47; CI 1.00-12.07), use of a gas cooker in houses (OR = 2.21; CI 1.03-4.70), and the age of the respondents (0.98; CI 0.96-1.00). The study showed that as distance from the plant increased, the incidence of reported gastrointestinal disorders declined. Living in the vicinity of a sewage treatment plant favours the occurrence of gastrointestinal symptoms among the local residents.

Full text

Introduction
Sewage treatment plants protect water resources
against pollutants and constitute an important com-
ponent of environmental protection. Nevertheless, the
premises of such plants accumulate both chemical
contaminants (including heavy metals, aromatic
hydrocarbons, and aromatic solvents) as well as biological
contaminants (viruses, bacteria, fungi, parasites, and
protozoa), which are a common cause of diseases,
including gastroin-testinal disorders [1]. This poses
a serious epidemiolo-gical threat, especially to the
Pol. J. Environ. Stud. Vol. 26, No. 1 (2017), 127-136
Original Research
Impact of a Sewage Treatment Plant
on Health of Local Residents:
Gastrointestinal System Symptoms
Aleksandra Jaremków1*, Łukasz Szałata2, Barbara Kołwzan2,
Izabela Sówka2, Jerzy Zwoździak2, Krystyna Pawlas1, 3
1Department of Hygiene, Medical University of Wrocław,
J. Mikulicza-Radeckiego 7, 50-368 Wrocław, Poland
2Faculty of Environmental Engineering, Wrocław University of Technology,
Wybrzeże Wyspiańskiego St. 27, 50-370 Wrocław, Poland
3Institute of Occupational Medicine and Environmental Health,
Kościelna 13, 41-200 Sosnowiec, Poland
Received: 14 July 2016
Accepted: 20 August 2016
Abstract
The aim of this study was to evaluate the impact of a sewage treatment plant on the occurrence of
gastrointestinal symptoms among the local residents. A survey was conducted on two populations: one from
the vicinity of the sewage treatment plant (the exposed group: 586 people), and the other from outside the
impact area of the plant (the control group: 502 people). The research area was divided into distance zones
from the plant (A, B, C). The questionnaire included questions about the occurrence of gastrointestinal
disorders. Compared with the control group, the local residents reported more often: nausea, vomiting, and
frequent diarrhea. Occurrences of gastrointestinal disorders were associated with air pollution by pathogenic
staphylococci (OR~7) and odours (OR = 7.34; Cl 3.43-15.72) emitted by the plant, and also living in zone
A vs. zone C (OR = 3.47; CI 1.00-12.07), use of a gas cooker in houses (OR = 2.21; CI 1.03-4.70), and the
age of the respondents (0.98; CI 0.96-1.00). The study showed that as distance from the plant increased, the
incidence of reported gastrointestinal disorders declined. Living in the vicinity of a sewage treatment plant
favours the occurrence of gastrointestinal symptoms among the local residents.
Keywords: environmental exposure, gastrointestinal disorders, health, sewage
*e-mail: aleksandrajaremkow@wp.pl
DOI: 10.15244/pjoes/64793

128 Jaremków A., et al.
employees of such plants who come in direct contact with
sewage [2].
The sewage treatment process involves the emission
of odours and biological agents in the form of bioaerosol.
Depending on the direction and strength of the wind, the
season of the year, and topography of the area where the
plant is located, the emission of pollutants may extend
beyond the plant premises, which also poses a risk of
exposure to the residents living in the vicinity of the plant
[3-4]. Pollutants can get into the gastrointestinal tract,
initiating inammatory reactions (e.g., Gram-negative
bacteria, staphylococci, and endotoxins) and consequently
causing disturbances such as nausea, vomiting, diarrhea,
and abdominal pain [5]. Depending on individual
susceptibility, odours may also cause gastrointestinal
disorders, as evidenced, for example, by the studies of
Aatamila et al. [6] (people with high olfactory sensitivity
reported diarrhea more often than the other respondents).
The impact of odours on the occurrence of gastrointestinal
disorders remains a contentious issue because the
underlying mechanisms behind such symptoms are not
fully understood [7].
The aim of this study was to evaluate the impact
of a sewage treatment plant on the occurrence of
gastrointestinal disorders among the local population.
So far, the issue of the impact of pollution emitted from
the sewage treatment plant on the gastrointestinal tract
of nearby residents has not been thoroughly analysed.
Instead, the literature focuses on occupational exposure [1-
2, 5]. Just a few scientists, i.e., Herr et al. [8] and Aatamila
et al. [6], have conducted research on the health effects of
living in the vicinity of such plants. However, nobody had
previously analysed the impact of odour pollutants as well
as microbial pollutants emitted from sewage treatment
plants on the incidence of gastrointestinal disorders
among the local population. Due to the increasing number
of sewage plants operating in Poland, the problem of plant
pollutant emissions may intensify, which makes the above
issue very topical [9].
Material and Methods
Characteristic of the Sewage
Treatment Plant
The study was conducted in the vicinity of the
mechanical-biological sewage treatment plant. Wastewater
treatment facilities were only partially hermetic – in
the mechanical part, without clariers (primary and
secondary) and bioreactors. In the biological treatment
process the activated sludge method was used.
Survey Research
A review of the documentation on the conditions
existing at the site of the examined municipal sewage
treatment plant enabled the authors to draw up an original
survey based on a survey used in CESAR studies (PHARE-
CESAR STUDY – international studies on children’s
respiratory systems in the countries of Central Europe)
[10]. The survey questions concerned potential symptoms
and diseases of the gastrointestinal tract characteristic of
the composition of bioaerosol from a sewage plant: “What
are your current diseases or gastrointestinal disorders?”
We asked about nausea, vomiting, and frequent diarrhea.
The respondents could choose from the following answers:
Yes (medical opinion) – related to diseases diagnosed by
a doctor, Yes (my own opinion) – concerned ailments
suffered by the respondent but undiagnosed by a doctor,
and No – lack of ailments. The questionnaire also included
questions on living conditions (type of residential building,
source of heating, use of a gas cooker, presence of pets at
home, indoor dampness, smoking of cigarettes in the at,
and exposure to car fumes).
The survey was conducted on two populations of
residents from neighbouring villages, one living in the
vicinity of the examined treatment plant (the exposed
group) and the other belonging to the same commune but
living outside the impact area of the plant and constituting
the control group. Such a choice of both populations
allowed for the elimination of potential confounders
related to climate and weather conditions, eating habits,
and general air pollution around the place of residence.
The analysed populations did not differ in this regard.
The estimated size of the sample, with knowledge
of the age structure of the inhabitants (approx. 5% of
children aged 3-10 years and approx. 80% of adults) of
both villages, with the populations of approximately
11,000 inhabitants in the impact area and 5,000 inhabitants
in territory not impacted by the plant, amounted to,
respectively, 590 and 504 people. The selection process
for both groups was based on systematic sampling. The
interviewers selected every 10th at from an address list
(from the local municipal ofce).
The examined populations were divided into two
subgroups: adults (aged 20-65 years) and children (aged
3-10 years). The analysis excluded teenagers and the
elderly due to the introduction of possible confounders
(disturbances associated with adolescence and senile
diseases).
Out of the 1,094 people who took part in the study, six
individuals were rejected due to non-fullment of the age
requirements. Thus, the nal number of the respondents
was as follows: 586 people from the exposed group and
502 people from the control group (in total 1,088 people).
Following the collection of all surveys, a computer
database was established containing the information
provided in the survey prepared within the framework of
the present epidemiological study.
Free and informed consent of the participants or their
legal representatives was obtained, and the study protocol
was approved by the Bioethics Committee of the Wroclaw
Medical University, Wrocław, Poland (approval no. KB
764/2012).

129
Impact of a Sewage Treatment...
Olfactometric and Microbiological Tests
Olfactometric measurements were performed in
summer and winter according to German VDI 3940
guidelines [11] and covered an area up to 1.5 km east of
the sewage treatment plant and 2.5 km northwest of the
plant. The measurement unit was the frequency of odours.
Microbiological measurements were performed in all
seasons (summer, in July 2011; autumn, in November
2011; winter, in March 2012; and spring in April 2012)
and covered an area up to 0.5 km from the examined
sewage treatment plant (the sampling places: 100 m,
180 m, 200 m, 225 m, 250 m, 350 m, 400 m, and 500
m – distances from the sewage treatment plant). The
tests included indicator microorganisms (psychrophilic
and mesophilic bacteria, Pseudomonas uorescens,
actinomycetes, staphylococci, and moulds) in accordance
with the applicable Polish Standards [12-13] and also
indicator bacteria from the Enterobacteriaceae family.
The examination was performed using the sedimentation
method. Petri dishes (9 cm diameter) with an appropriate
agar medium for 30 min were placed at a height of 130
cm above ground level. Then, depending on the type of
microorganisms and the used agar medium, the samples
were incubated at 10-44ºC for 1-7 days:
– Psychrophilic bacteria: agar PCA with cycloheximide,
22ºC, 3 days.
– Mesophilic bacteria: agar PCA with cycloheximide,
37ºC, 1 day.
– Yeast-like: Sabouraud with TTC, 26ºC, 3-5 days.
– Molds: Sabouraud with chloramphenicol, 26ºC, 3-5
days.
– Actinomycetes: Pochon, 26ºC, 3-5 days.
– Pseudomonas uorescens: King B cykloheksamidem,
4ºC, 7 days or 26°C, 3-5 days.
– α- and ß-haemolytic staphylococci: Columbia + 5%
sheep blood, 37ºC, 2 days.
– Mannitol-positive and mannitol-negative staphylo-
cocci: Chapman, 37ºC, 1-2 days.
– Coliforms, Escherichia coli: Endo-LES, 37/44ºC, 1 day.
After this time the colonies were counted and iden-
tied. Concentrations of microorganisms were calculated
according to Omelianski’s formula, modied by Gogo-
beridze [13]:
…where x is the average number of microorganisms per
1 m3 air [CFU/m3] (from three repeated measurements), a
is the number of microorganisms per plate, πr2 is the plate
surface (cm2), and t is exposure time (min). The above
formula is based on the assumption that within 5 minutes
the same number of microorganisms settles on the surface
of 100 cm2 as in the air volume: 10 m3.
The obtained data were entered into the computer
database, assigning their location to the nearest place of
residence of the respondents (address data).
Olfactometric tests showed that the impact area of the
examined sewage treatment plant extended up to 1.5 km
from the plant, with the highest air pollution rates recorded
within 0.5 km of its boundary (according to olfactometric
and microbiological tests). On the basis of these ndings,
the area around the sewage treatment plant was divided
into three zones: A, B, and C. Zone A (highest air pollution)
extended up to 0.5 km from the plant, zone B (average air
pollution) extended from 0.5 km to 1.5 km from the plant,
and zone C (control group) covered an area outside the
impact rage of the plant (more than 2 km away).
At the time of conducting the surveys, neither the
respondents nor the interviewers knew which zones
corresponded to individual participants.
Statistical Analysis
Statistical analysis was performed using Statistica 10.0
for Windows software. The incidence of gastrointestinal
disorders among children and adults was compared
between the examined populations (the controls/the
exposed) and with respect to the distance from the sewage
treatment plant (divided into zones: A, B, and C). For this
purpose, Pearson’s chi-squared test was performed. The
impact of risk factors on the incidence of gastrointestinal
disorders (conrmed by medical opinion) was assessed
using logistic regression analysis (single-factor model –
microorganisms and odours; multi-factor model – other
risk factors). The odds ratios (OR) were also calculated
with the corresponding 95% condence intervals (CI).
The following were classied as risk factors: living in
zone A as opposed to zone C (A vs. C), living in zone B
as opposed to zone C (B vs C), age, period of residence,
type of residential building, exposure to tobacco smoke,
use of a gas cooker, type of heating, indoor dampness,
ownership of pets, exposure to car exhaust fumes (number
of cars passing by the house), high concentrations of
microorganisms in the air, and odours (frequency of
odours in summer and winter). The adopted level of
statistical signicance was p<0.05 for all analyses.
Results
Characteristics of Air Pollution (Microorganisms
and Odours) around the Examined Sewage
Treatment Plant
Within 0.5 km of the examined sewage treatment
plant we found pathogenic staphylococci (α-haemolytic,
β-haemolytic, mannitol-positive, and mannitol-
negative; Table 1). The highest concentrations were
recorded for β-haemolytic staphylococci (1180 CFU/
m3) and α-haemolytic staphylococci (826 CFU/m3). At
most measurement points the recorded staphylococci
concentrations exceeded Polish safe air quality standards
(respectively >50 and >25 CFU/m3 [13]).
By contrast, concentrations of microorganisms
commonly found in the environment (Pseudomonas

130 Jaremków A., et al.
uorescens, psychrophilic and mesophilic bacteria,
actinomycetes, molds) indicated mostly low or medium
levels of air pollution according to Polish standards
(respectively: lack, <3,000, <100, <5,000 CFU/m3) [12-
13].
Concentrations of yeast-like fungi remained at a level
of 0-524 CFU/m3.
No bacteria of faecal origin were found in the air of the
area covered by microbiological analysis.
According to olfactometric tests, the odours emitted
from the sewage treatment plant were perceptible even at
a distance of approx. 2 km from the plant. The recorded
frequency of odours was signicantly higher in summer
(Fig. 1a) than in winter (Fig. 1b). The frequency of odours
coming from the plant in zone A (closest proximity to
the plant) reached up to 92% (in summer). In zone B the
measured frequency of odours ranged from 0% at the end
of zone B to 78% (in summer) at the boundary of exposure
zones A and B. In the area of residence of the control
group, the frequency of odours reached up to 33%. The
measured odour rates correlated with distance from the
sewage treatment plant: the frequency of odours decreased
as the distance from the plant increased (Fig. 1).
Study Population
The characteristics of the examined population,
divided into the control group and the exposed group, are
shown in Table 2. In both subpopulations there is a similar
number of men and women. In the control group and the
exposed group the children account for, respectively,
25.5% and 28.8%, whereas the adults account for 74.5%
and 71.2%. Among people classied to the individual
zones, the smallest percentage of respondents consisted of
inhabitants of zone A: 8.1% (zone B: 43.6% and zone C:
46.1%).
Most people from the exposed group live in blocks
of ats with central heating, whereas the control group
is dominated by residents of single-family houses, who
use different types of heating (gas stove, coal stove, and
replace). Compared to the control group, a predominant
percentage of people from the exposed group smoke at
home. On the other hand, pet owners were mostly people
from outside the area impacted by the sewage treatment
plant (control group). No differences were found between
the examined populations in terms of indoor dampness
and exposure to car exhaust fumes.
Group Division: Control/Exposed
Compared to the control group, a predominant
percentage of children from the exposed group reported
nausea and vomiting. Also, among adult inhabitants of
the impact area there were signicantly more occurrences
of nausea and frequent diarrhoea compared to the control
Table 1. Concentrations of microorganisimsa (minimum/
maximum) in the air in the vicinity of a sewage treatment plant
(up to 0.5 km from the plant).
Microorganisms Concentrations in the air [CFU/m3]
Mean Min. Max.
psychrophilic bacteria 2076 576 4087
mesophilic bacteria 1005 52 3354
actinomycetes 56 0 183
α-haemolytic
staphylococci 252 26 826
β-haemolytic
staphylococci 98 0 1180
mannitol-positive
staphylococci 101 0 288
mannitol-negative
staphylococci 59 0 354
molds 4148 217 9432
yeast-like fungi 177 0 524
aconcentrations of microorganisms determined in three
repeated measurements
Measurement periods: summer, July 2011; autumn,
November 2011; winter, March 2012; and spring, April 2012
Fig. 1. The incidence of odours in distance zones in the summer
a) and in the winter b).

131
Impact of a Sewage Treatment...
group. The indicated symptoms were conrmed by
medical diagnosis as well as independent opinion of the
respondents (Figs 2a-b).
Zone Division: A, B, and C
Among children, signicant differences between the
zones concerned the prevalence of nausea, vomiting, and
frequent diarrhoea. The above-mentioned symptoms,
conrmed by medical diagnosis, dominated in zone A,
and their reportability decreased as the distance from
sewage treatment plant increased (Fig. 3a). The situation
was similar with regard to adults, but only in the case of
vomiting were there no signicant differences reported
between the examined zones.
However, according to an independent opinion of
the respondents, symptoms such as nausea and vomiting
in children, and only nausea in adults, appeared most
frequently in zone B (Fig. 3b).
The Impact of Microbial and Odorous Pollution
on the Incidence of Gastrointestinal Disorders
In order to examine the effects of microbial air
pollution on the reported gastrointestinal disorders in t
he immediate vicinity of the sewage treatment plant
(zone A), the occurrence of such disturbances was
compared between respondents exposed to con-
centrations of microorganisms exceeding Polish air quality
standards (total bacteria >3,000 CFU/m3; actinomycetes
Table 2. Characteristics of the study population.
Characteristics
Control (Na = 502)
CH: 128
A: 374
Exposed (N = 586)
CH: 169
A: 417
nb%cn %
Sex
Female CHd72 56.2 80 47.3
Male 56 43.8 89 52.7
Female Ae207 55.3 232 55.6
Male 167 44.7 185 44.4
Exposure to tobacco smoke in the at
(missing 1)
CH 21 16.4 38 22.6
A 69 18.5 146 35.0
Living in blocks of ats CH 17 13.3 150 88.8
A 82 21.9 407 97.6
Use of gas cooker CH 115 89.8 93 55.0
A 309 82.6 298 71.5
Heating (central heating)
(missing 15)
CH 69 53.9 167 98.8
A 248 66.3 411 98.6
Dampness in the at (missing 2) CH 17 13.3 28 16.8
A 32 8.6 46 11.0
Ownership of pets (missing 5) CH 70 54.7 64 38.8
A 220 58.8 152 36.5
Exposure to car fumes (missing 3) CH 39 30.5 54 32.3
A 133 35.6 147 35.3
Zone A CH - - 43 49.4
A - - 44 50.6
Zone B CH - - 120 25.3
A - - 354 74.7
Zone C CH 128 25.5 - -
A 374 74.5 - -
aall respondents from studied population, bnumber of respondents, cproportion of respondents, dchildren (3-10 years)
eadults (20-65 years)

132 Jaremków A., et al.
>100 CFU/m3; α-haemolytic staphylococci and mannitol-
positive staphylococci >25 CFU/m3; β-haemolytic
staphylococci and mannitol-negative staphylococci >50
CFU/m3) and the control group.
Among the analysed microorganisms, only
α-haemolytic staphylococci (OR = 6.76; CI 3.17-14.45)
and mannitol-positive staphylococci (OR = 7.22; CI
3.37-15.45) had a signicant impact on the incidence of
gastrointestinal disorders among inhabitants of zone A.
The research has also shown that the incidence of
gastrointestinal disorders in the immediate vicinity of the
sewage treatment plant (zone A) was closely associated
with exposure to odours, issued by the plant in summer
(OR = 7.34; CI 3.43-15.72). By contrast, odour emissions
in winter had no impact on the incidence of the indicated
symptoms among the respondents. Similarly, in the case of
zone B inhabitants no correlation was found between the
reported gastrointestinal disorders and odour emissions
(either in summer or winter) from the plant.
The Impact of Different Risk Factors
on the Incidence of Gastrointestinal Disorders
Among the Respondents
The model shown in Table 3 was used to analyse the
impact of coexisting, potential health risks on the incidence
of gastrointestinal conditions among all respondents
(multifactorial analysis). The reported gastrointestinal
disorders depended to a signicant degree on: place of
residence in zone A relative to zone C (on the border of
statistical signicance), age of the respondents, and use
of a gas cooker. In the case of other factors, no correlation
was found with the reported gastrointestinal disorders.
A stratied model for children is presented in Table 4
and for adults in Table 5. The occurrence of gastrointestinal
disorders among children was signicantly associated
with the use of a gas cooker and having pets. For adults,
the type of a residential building had a signicant impact
on reported symptoms.
Discussion
Both microbiological and olfactometric tests show
that the area of greatest air pollution extended to 0.5 km
from the examined sewage treatment plant. This is
consistent with the results of studies published by
German researchers, who reported high concentrations of
microorganisms (>105 CFU/m3) as far as 0.55 km away
from the analysed composting plant [8]. On the other
hand, Albrecht et al. [3] demonstrated that emissions of
microbiological pollutants may also extend beyond 0.5
km (even up to 0.8-1.4 km) from the plant depending on
the weather conditions, topography, process technology
of the plant, and the methods of control of pollutant
emissions. The highest concentrations of microorganisms
reported by them concerned actinomycetes and
thermotolerant fungi. By contrast, the results of our
research indicate that the most dangerous air contaminants
were staphylococci (α-haemolytic and mannitol-positive),
whose concentrations signicantly exceeded safe air
quality standards [12-13]. The presence of staphylococci
in outdoor air samples is a natural phenomenon because
they belong to environmental bacteria; however, their
elevated concentrations are dangerous to human health
and may indicate the presence of an anthropogenic emitter
(e.g., a sewage treatment plant) [14]. On the other hand,
the microorganisms commonly found in the environment
did not constitute a health risk for the examined population
because their concentrations were within the range
showing low or medium air pollution. Compared with
literature data, their number was lower than in the vicinity
of similar sewage treatment plants [15].
In the literature there are few studies that analyse the
frequency of odours around such plants. According to our
research, the emission of odours extended up to approx.
2 km from the plant, covering a range from 92% in the
zone adjacent to the plant (zone A) to 0% at the end of
zone B. Odours were also perceived in the zone inhabited
Fig. 2. Statistically signicant differences of gastrointestinal
disorders in children and adults between the control and the
exposed group (a) – “Yes (medical opinion)”, b) – “Yes (my own
opinion)”. All presented data: p<0.05.
Fig. 3. Statistically signicant differences of gastrointestinal
disorders in children and adults by distance zone (a) – “Yes
(medical opinion)”, b) – “Yes (my own opinion)”). p<0.05 zone
A vs zone B vs zone C (marked as “a”); p < 0.05 zone A vs zone
B and zone A vs zone C (marked as “b”).

133
Impact of a Sewage Treatment...
by the control group, where their frequency reached up
to 33%. Their source could be local livestock farms. By
way of comparison, German test results of air pollution in
the vicinity of a composting plant demonstrate that odour
was perceptible up to approx. 870 m from the plant. At
this distance, the frequency of odour perception was 10-
30% [4].
In this study there was an increase in the incidence
of gastrointestinal disorders in the exposed group
compared to the control group. In the group of children
this concerned nausea and vomiting, whereas in adults
it concerned nausea and frequent diarrhoea. All of the
reported ailments, conrmed by medical diagnosis,
correlated with the distance from the sewage treatment
plant. They appeared most frequently in zone A, gradually
decreasing with increasing distance from the plant. Only
in the case of independent opinion of the respondents
did nausea and vomiting dominate in zone B. The
resulting differences may arise from the fact that not all
gastrointestinal disorders were diagnosed by a medical
professional; some of the symptoms were treated with
home remedies. A correlation between the incidence
of gastrointestinal symptoms and the distance from the
treatment plant was conrmed by German studies [8],
which analysed the impact of pollutants emitted from a
composting plant on the health of nearby residents. On
the other hand, according to Finnish researchers, due to
technical diversity of the ve analysed sewage treatment
plants, no correlation was found between the reported
gastrointestinal disorders and the distance from the plant
[6].
The symptoms reported by the respondents are
consistent with gastrointestinal disorders also occurring
among employees of sewage treatment plants. According
to a study by Abd El-Wahab et al., compared to the
unexposed group, the employees reported signicantly
more frequently: diarrhoea, vomiting, abdominal colics,
and dyspepsia (in our study we did not ask the respondents
about abdominal colics, dyspepsia) [2]. Abdominal
pain may be the result of direct contact with sewage,
and therefore exposure to adenoviruses, rotaviruses,
noroviruses, enteroviruses, and the Helicobacter pylori
bacterium [16]. Similar results were also obtained by
Dutch researchers, according to whom sewage plant
employees reported gastrointestinal symptoms (nausea,
vomiting, diarrhoea, and loss of appetite) approx.
twice as often as ofce workers [17]. The similarity of
reported symptoms between residents of areas adjacent
to the sewage plant and the employees of such plants
demonstrates comparable exposure to sewage pollution.
This is all the more important since the employees come
in direct contact with sewage, therefore microbes most
commonly spread via the gastrointestinal tract while the
health risks of people living in the vicinity of the sewage
Table 3. Odds ratios (OR) and 95% condence intervals (CI) for
reported gastrointestinal disorders relative to the risk factors –
the whole population (Na = 1,088); R2
Negelkerke’a
b = 0.11.
Table 4. Odds ratios (OR) and 95% condence intervals (CI) for
reported gastrointestinal disorders relative to the risk factors –
children (Na = 297); R2
Nagelkerke’a
b = 0.19.
Risk factors OR 95% CI pc
Zone B vs. Zone C 1.53 0.54-4.36 n.sd
Zone A vs. Zone C 3.47 1.00-12.07 0.050
Female 1.10 0.64-1.87 n.s
Age 0.98 0.96-1.00 0.040
Period of residence 0.99 0.95-1.03 n.s
Type of residential
building: block of ats 2.05 0.83-5.04 n.s
Exposure to tobacco
smoke 0.64 0.33-1.28 n.s
Using a gas cooker 2.21 1.03-4.70 0.040
Type of heating in the
house 0.76 0.25-2.30 n.s
Presence of moisture in the
house 1.22 0.58-2.58 n.s
Owner of pets 0.74 0.42-1.28 n.s
Exposure to car fumes 0.72 0.39-1.36 n.s
Odours 0.95 0.39-2.28 n.s
aall respondents from studied population
bgeneralized coefcient of determination
clevel of statistical signicance
dnot signicant
Risk factors OR 95% CI pc
Zone B vs. Zone C 3.15 0.64-15.49 n.sd
Zone A vs. Zone C 4.50 0.69-29.30 n.s
Female 1.12 0.50-2.50 n.s
Age 1.01 0.83-1.24 n.s
Period of residence 0.92 0.76-1.10 n.s
Type of residential
building: block of ats 1.18 0.37-3.73 n.s
Exposure to tobacco
smoke 0.44 0.13-1.52 n.s
Using a gas cooker 5.36 1.45-19.74 0.011
Type of heating in the
house 0.70 0.15-3.14 n.s
Presence of moisture in the
house 0.85 0.28-2.59 n.s
Owner of pets 0.34 0.13-0.87 0.024
Exposure to car fumes 0.96 0.37-2.46 n.s
Odours 1.04 0.25-4.25 n.s
anumber of children from studied population
bgeneralized coefcient of determination
clevel of statistical signicance
dnot signicant

134 Jaremków A., et al.
plant are related to their exposure to bioaerosols in the air
(the air droplet transmission route).
The symptoms reported by the respondents from
zone A were closely associated with exposure to the
highest concentration of staphylococci (α – haemolytic:
OR = 6.76; CI 3.17-14.45 and mannitol-positive: OR =
7.22; CI 3.37-15.45) in the air. Of these bacteria, e.g.,
Staphylococcus aureus is responsible for the occurrence
of gastrointestinal disorders (nausea, vomiting, diarrhoea,
and abdominal pint) – mostly as a result of consuming
contaminated food. However, sometimes the above
symptoms are caused by exposure to high concentrations
of staphylococci in the air. An inammatory reaction takes
place, whose main symptom is a rise in body temperature,
which is typically accompanied by respiratory and/or
gastrointestinal problems [18]. One US study reported a
minor increase in the prevalence of drug-resistant strains
of Staphylococcus aureus in the nasal cavity and on the
skin of employees in contact with sewage compared to the
control group; however, this indicates the existence of a
real health risk associated with the emission of pathogens
[19].
Lack of immunological testing among the residents
living in the vicinity of the sewage treatment plant which
would conrm the obtained relationship between exposure
to pathogenic staphylococci and reported symptoms was a
limitation of our study, but this is a good start to further
research.
In the present study we also noticed a correlation
between the reported gastrointestinal disorders among
the inhabitants of the immediate vicinity of the sewage
treatment plant (zone A) and the exposure to odours
emitted from the plant in summer (OR = 7.34; CI
3.43-15.72). This is in line with studies carried out by
Aatamila et al. [6], according to which people sensitive to
unpleasant smells had a higher incidence of diarrhoea than
the other respondents. On the other hand, the incidence of
nausea and vomiting did not depend on either sensitivity
or olfactory irritability. However, German studies conrm
a correlation between a feeling of nausea and odour
nuisance [20].
The mechanisms of initiation of gastrointestinal
disorders by odours have not yet been fully understood.
According to Herr [20], the incidence of nausea may be
associated with exposure to the odour of decomposing
organic material, which is explained by an associative
effect between an unpleasant smell and the place of its
origin (e.g., faeces, rotten leftovers, etc.). Odours may
also irritate organs, resulting in abdominal pain, nausea,
and diarrhoea. In people characterised by olfactory
hypersensitivity (MSC - multiple chemical sensitivity), the
occurrence of such symptoms can also be of psychogenic
nature (fear of the effect of odours, individual symptomatic
response to a stimulus) [7].
Gastrointestinal disorders may also occur as a result of
exposure to endotoxins, which are often recorded within
such plants. According to Rylander [5], endotoxins can
be deposited in the gastrointestinal tract, thus starting an
inammatory response in the intestinal mucosa, which
causes gastrointestinal symptoms such as abdominal pain
and diarrhoea. The results of a Dutch research study suggest
that when endotoxin concentration in the air ranged from
50-200 EU/m3, the risk of diarrhoea among sewage plant
employees was approximately 1.5 times higher than in the
unexposed group [17]. Also, Danish researchers found that
the risk of experiencing gastrointestinal disorders (nausea
and diarrhoea) increased with increased concentration of
endotoxins in the air [21]. In the present study, we did not
measure the concentration of endotoxins in the air, which
undoubtedly is a limitation; however, given the increased
incidence of reported gastrointestinal disorders in the
exposed group as compared to the control group, it can
be assumed that the cause of their occurrence was also
exposure to endotoxins emitted from the sewage treatment
plant.
Among the co-occurring health risks, living in
zone A was associated with a higher probability of
gastrointestinal disorders compared to the control group.
This can be explained by the results of microbiological
and olfactometric measurements, according to which this
was the area with the highest pollution rates. The results
of studies by Herr [8] also show that living at a distance
of up to approximately 0.5 km from the composting
plant (bacteria concentration in the air >105 CFU/m3)
was associated with a signicant risk of occurrence of
gastrointestinal disorders.
Table 5. Odds ratios (OR) and 95% condence intervals (CI)
for reported gastrointestinal disorders relative to the risk factors
– adults (Na = 791); R2
Nagelkerke’a
b = 0.09.
Risk factors OR 95% CI pc
Zone B vs. Zone C 0.81 0.20-3.21 n.sd
Zone A vs. Zone C 1.69 0.28-10.13 n.s
Female 1.24 0.58-2.64 n.s
Age 1.02 0.99-1.05 n.s
Period of residence 0.99 0.95-1.04 n.s
Type of residential building:
block of ats 8.80 1.73-44.84 0.009
Exposure to tobacco smoke 0.69 0.29-1.64 n.s
Using a gas cooker 1.15 0.43-3.08 n.s
Type of heating in the house 1.34 0.22-8.07 n.s
Presence of moisture in the
house 1.86 0.65-5.29 n.s
Owner of pets 1.33 0.63-2.81 n.s
Exposure to car fumes 0.53 0.22-1.29 n.s
Odours 1.05 0.31-3.49 n.s
anumber of adults from studied population
bgeneralized coefcient of determination
clevel of statistical signicance
dnot signicant

135
Impact of a Sewage Treatment...
The use of a gas cooker was another factor found to
be signicant in such disorders (in the whole population,
especially among children). The health risks resulting
from gas cooker use were connected with the emission
of carbon monoxide and nitrogen dioxide. In the case
of poisoning with the rst of said chemicals, the victims
suffer primarily from neurological and cardiac disorders,
which can be accompanied by nausea and vomiting (early
stage poisoning) [22]. However, prolonged exposure to
high concentrations of nitrogen dioxide usually cause
respiratory problems and eye irritations. At a later stage,
the affected individuals may also suffer from cardiac and
neurological disorders, but gastrointestinal disorders are
not among characteristic symptoms of nitrogen dioxide
poisoning. In one study by English researchers, a correlation
was found between the incidence of diarrhoea among
children and exposure to nitrogen dioxide. However, the
mechanism behind the above result is not clear; therefore,
researchers suggested that the obtained correlation could
have been accidental [23]. Due to the small number of
reports in the literature associating exposure to nitrogen
dioxide with the occurrence of gastrointestinal disorders,
the authors of this study agree with the presented view.
Age was another important factor associated with
the occurrence of gastrointestinal disorders among the
respondents. In contrast to the previously presented risk
factors (residence in zone A as opposed to zone C and use
of a gas cooker), a decrease in this parameter increased the
probability of the appearance of gastrointestinal symptoms
(OR<1). Thus, the younger the respondents were, the more
often they became aficted with gastrointestinal diseases.
This may be due to the less developed immune system
in children as compared to adults [24]. Besides, children
are still learning proper hygienic practices, hence they are
more likely than adults to make related mistakes that may
cause gastrointestinal disorders, such as lack of the habit
of washing hands before eating and licking and putting
dirty objects (e.g., toys) as well as their hands into their
mouths [25].
Our research also shows that children with pets reported
gastrointestinal disorders less frequently than children
who do not have contact with pets. The existence of the
indicated dependence can be explained by the so-called
hygiene hypothesis, according to which contact of the
body with microbes has a benecial effect on the immune
system whereas excess purity leads to the development of
many different diseases (not only allergic) [26].
Gastrointestinal disorders in adults occurred more
often among inhabitants of blocks of ats than detached
houses. It can be assumed that in smaller-area houses (i.e.,
blocks of ats), air pollution resulting from poor exchange
of indoor air occurred more frequently (rare airing due to
social reservations about the inux of pollution from the
sewage treatment plant through the windows). Bad indoor
air quality can cause several non-specic symptoms,
including gastrointestinal disorders (nausea, vomiting,
diarrhoea; sick building syndrome) [27].
Conclusion
The results of our study show that living in the vicinity
of the analysed sewage treatment plant is associated with
an increased risk of the occurrence of gastrointestinal
disorders among the population. The health impact area
of the sewage treatment plant extended up to approx.
2 km from its border, including the village where the
plant was located. The study showed that as the distance
from the sewage treatment plant increased, the percentage
of gastrointestinal incidents decreased (zone A > zone
B > zone C). Gastrointestinal disorders were reported
most often at a distance of up to 0.5 km (zone A) from the
examined sewage treatment plant, which was related to the
highest rates of air pollution in this area (microbiological
pollutants and odours). Among the microorganisms
identied in the air, pathogenic α-haemolytic and
mannitol-positive staphylococci had a signicant effect
on the reported gastrointestinal disorders in the immediate
vicinity of the sewage treatment plant. The emission of
odours in summer also favoured the occurrence of such
disorders. Due to the prevailing morbidity rate (especially
of children) among the population living in the vicinity
of the sewage plant, corrective actions should be taken to
limit/eliminate pollutant emissions (e.g., hermetization of
clariers and bioreactors).
Acknowledgements
This study was funded by the Wrocław University of
Technology as commissioned by Faculty of Environmen-
tal Engineering (No. 60-039-2). We thank the residents for
their participation in the study.
References
1. AL-BATANONY M.A., EL-SHAFIE M.K. Work-Related
Health Effects among Wastewater Treatment Plants Workers.
Int. J. Occup. Environ. Med., 2 (4), 237, 2011.
2. ABD EL-WAHAB E.W., EASSA S.M., LOTFI S.E., EL
MASRY S.A., SHATAT H.Z., KOTKAT A.M. Adverse
health problems among municipality workers in alexandria
(egypt). Int. J. Prev. Med. 5 (5), 545, 2014.
3. ALBRECHT A., FISCHER G., BRUNNEMANN-STUBBE
G., JÄCKEL U., KÄMPFER P. Recommendations for study
design and sampling strategies for airborne microorganisms,
MVOC and odours in the surrounding of composting facili-
ties. Int. J. Hyg. Environ. Health, 211 (1-2), 121, 2008.
4. FISCHER G., ALBRECHT A., JÄCKEL U., KÄMPFER P.
Analysis of airborne microorganisms, MVOC and odour in
the surrounding of composting facilities and implications for
future investigations. Int. J. Hyg. Environ. Health, 211 (1-2),
132, 2008.
5. RYLANDER R. Health effects among workers in sewage
treatment plants. Occup. Environ. Med., 56 (5), 354, 1999.
6. AATAMILA M., VERKASALO P.K., KORHONEN M.J.,
SUOMINEN A.L., HIRVONEN M.R., VILUKSELA
M.K., NEVALAINEN A. Odour annoyance and physical

136 Jaremków A., et al.
symptoms among residents living near waste treatment cen-
tres. Environ. Res., 111 (1), 164, 2011.
7. OIAMO T.H., LUGINAAH I.N., BAXTER J. Cumulative
effects of noise and odour annoyances on environmental and
health related quality of life. Soc. Sci. Med. 146, 191, 2015.
8. STILIANAKIS N.I., BOEDEKER R.H., EIKMANN T.F.
Effects of bioaerosol polluted outdoor air on airways of
residents: a cross sectional study. Occup. Environ. Med., 60
(5), 336, 2003.
9. CENTRAL STATISTICAL OFFICE OF POLAND. En-
vironmental protection 2015. Regional and Environmen-
tal Surveys Department. Report Published date: 2015
http://stat.gov.pl/download/gfx/portalinformacyjny/en/
defaultaktualnosci/3303/1/7/1/environment_2015.pdf
(accessed 24 January 2016).
10. ZŁOTKOWSKA R., JAŹWIEC-KANYION B., KRUŻEL-
MENDREK J., ZEJDA J. Air pollution and respiratory
health in children, results of a PHARE-CESAR study in
Poland. Proceedings of the Latvian Academy of Sciences, 52
(Supl.), 172, 1998.
11. VDI 3940 PART 3, Measurement of odour in ambient air
by eld inspections – Determination of odour intensity and
hedonic odour tone, Verein Deutscher Ingenieure, Berlin,
Beuth Verlag, Germany, 2010.
12. POLISH STANDARDS PN-89/Z-04111/02. Air purity
protection. Microbiological testings. Determination number
of bacteria in atmospheric air (imision) with sampling by
aspiration and sedimentation method (Ochrona czystości
powietrza. Badania mikrobiologiczne. Oznaczanie liczby
bakterii w powietrzu atmosferycznym (imisja) przy pobie-
raniu próbek metodą aspiracyjną i sedymentacyjną), Polski
Komitet Normalizacji, Miar i Jakości, Warsaw, Poland, 1989
[In Polish].
13. POLISH STANDARDS PN-89/Z-04111/03. Air purity
protection. Microbiological testings. Determination number
of the fungi in the atmospheric air (imision) with sampling
by aspiration and sedimentation method (Ochrona czystości
powietrza. Badania mikrobiologiczne. Oznaczanie liczby
grzybów mikroskopowych w powietrzu atmosferycznym
(imisja) przy pobieraniu próbek metodą aspiracyjną i sedy-
mentacyjną), Polski Komitet Normalizacji, Miar i Jakości,
Warsaw, Poland, 1989 [In Polish].
14. GANGULY S., MUKHOPADHAYAY S.K., BISWAS S.
Potential threat to human health from foodborne illness
having serious implications on public health- a Review.
IJCBS, 1, 65, 2012.
15. KORZENIEWSKA E., FILIPKOWSKA Z.,
GOTKOWSKA-PŁACHTA A., JANCZUKOWICZ W.,
DIXON B., CZUŁOWSKA M. Determination of emitted
airborne microorganisms from a BIO-PAK wastewater
treatment plant. Water Res. 43 (11), 2841, 2009.
16. VAN HOOSTE W., CHARLIER A.M., ROTSAERT P.,
BULTERYS S, MOENS G., VAN SPRUNDEL M., De
SCHRYVER A. Work-related Helicobacter pylori infection
among sewage workers in municipal wastewater treatment
plants in Belgium. Occup. Environ Med., 67 (2), 91, 2010.
17. SMIT L.A., SPAAN S., HEEDERIK D. Endotoxin exposure
and symptoms in wastewater treatment workers. Am. J. Ind.
Med., 48 (1), 30, 2005.
18. BYSTROŃ J., LIS E., BANIA J., MOLENDA J. 2008
Occurrence of methicillin-resistant genes in Staphylococcus
aureus strains. Acta Sci. Pol. Med. Vet., 7, 3, 2008.
19. ROSENBERG GOLDSTEIN R.E., MICALLEF S.A.,
GIBBS S.G., HE X., GEORGE A., SAPKOTA A.,
JOSEPH S.W., SAPKOTA A.R. Occupational exposure to
Staphylococcus aureus and Enterococcus spp. among spray
irrigation workers using reclaimed water. Int. J. Environ.
Res. Public Health., 11 (4), 4340, 2014.
20. HERR C.E.W., ZUR NIEDEN A., BOEDEKER R.H.,
GIELER U., EIKMANN T.F. Ranking and frequency of so-
matic symptoms in residents near composting sites with odor
annoyance. Int. J. Hyg. Environ. Health., 206 (1), 61, 2003.
21. UHBRAND K., SCHULTZ A.CH., MADSEN A.M.
Exposure to Airborne Noroviruses and Other Bioaerosol
Components at a Wastewater Treatment Plant in Denmark.
Food Environ. Virol., 3 (3), 130, 2011.
22. LEONDA I., MARSH R., MKILAHA I., GRIFFITHS A.
Carbon Monoxide Exposure during Cooking in Households:
A Case of Dar es Salaam City, Tanzania. JESE-A, 2, 31,
2013.
23. OZMERT E.N., KILIC M., YURDAKÖK K. Environmental
tobacco smoke: is it a risk factor for diarrhea in 6-18 months
old infants? Cent. Eur. J. Public Health. 16 (2), 85, 2008.
24. SIMON A.K., HOLLANDER G.A, MCMICHAEL A. Evo-
lution of the immune system in humans from infancy to old
age. Proc. Biol. Sci. 282 (1821), 20143085, 2015.
25. SLY L., BRUNE-DRISSE M.N. Children’s Vulnerability to
Their Environment. J. Environ. Immunol. Toxicol. 1 (2), 58,
2014.
26. SIRONI M., CLERICI M. The hygiene hypothesis: an
evolutionary perspective. Microbes Infect., 12, 421, 2010.
27. BODUR S. 2014 Epidemiology of indoor air pollution. J
Chest Dis. Crit. Care Med., 1, 41, 2014.